40 years ago, Garvie and his Australian co workers reported that the stress induced transformation of metastable tetragonal zirconia grains to the monoclinic symmetry could give rise to a powerful toughening mechanism. Their results even led them to consider zirconia systems as analogues of certain steels in terms of mechanical performances, while exhibiting a much superior corrosion resistance. This seminal paper generated extraordinary excitement in the ceramic community and led to a large variety of new applications. Transformation toughening is widely used in current zirconia materials, mostly in the form of yttria stabilized systems (Y-TZP) and results in an increase in strength and toughness when compared to non transformable ceramics such as alumina.
However, it is evident that zirconia ceramics still fail at low strains with a much larger scatter in the strength values than metals and require statistical approaches to failure. Here we describe in details the mechanical behavior laws of newly developed ceriadoped zirconia composites exhibiting a high degree of stress-induced transformation.
i) significant amount of transformation-induced plasticity without damage,
ii) very high flaw tolerance and
iii) almost no dispersion in strength data. They potentially open new application avenues in situations where the advantages of ceramics were dampened by their brittle failure behavior. In particular, the consequences of such behavior for dental implants and additive-manufactured structures are highlighted. The biocompatibility and bone integration of this material is also discussed.
About Dr. Chevalier:
Born in 1970, Jérôme Chevalier is currently full Professor at the National Institute of Applied Sciences, in Lyon (INSA-Lyon), France. After receiving his PhD in 1996 (Mechanical properties of biomedical grade zirconia), Jérôme Chevalier first became Ceramic Engineer in Saint Gobain Group. In 1997, he joined the National Institute of Applied Sciences, in Villeurbanne and became full Professor in 2004. Jérôme Chevalier is mainly recognized for his work on ceramics for healthcare applications, especially on zirconia as a biomaterial and on the development of innovative glass-ceramics and calcium phosphate ceramics for bone substitute applications. His research interests are also related to the mechanical behaviour laws of ceramics under different forms. He has been involved in a large number of European projects and has coordinated recently the LONGLIFE project, dealing with ceramic implants. He shows a strong involvement in partnerships with European companies in the field of medical devices. He has published more than 200 papers, holds 10 patents and has been cited more than 10.000 times. Jérôme Chevalier has been member of the ‘Institut Universitaire de France’ (2010-2015) and recently awarded by the French CNRS with the ‘Innovation Medal’ (2015). Jérôme Chevalier is currently one of the editors of the Journal of the European Ceramic Society. He is fellow of the European Ceramic Society (2017) and member of the World Academy of Ceramics (2018).